Window blinds comprise a plurality of parallel slats that typically are formed from metal, plastic or wood. Most metal blinds slats are curved from side to side to define a convex top surface and a concave bottom surface. The slats are supported in a substantially horizontal array by flexible vertically aligned ladders. Each ladder comprises an elongated flexible runner and a plurality of transverse supports. The ladders are interlaced with the slats of the window blinds such that the runners are disposed on opposite respective sides of the array of slats, and such that each respective slat is supported by one transverse support of each ladder. The runners of each ladder extend upwardly beyond the horizontal array of slats and into a channel.
A tilt control rod is rotatably mounted in the channel of the prior art window blinds. The tilt control rod includes drums mounted thereon at locations generally in line with the ladders of the window blind. The runners of each ladder extend into the channel and are wrapped in opposite directions around the drum. With this construction, rotation of the tilt control rod about its axis causes a corresponding rotation of the drums mounted thereto and associated longitudinal movement of the ladder runners mounted to each drum. In particular, rotation of the tilt control rod causes one runner in each ladder to move upwardly while the other moves downwardly. This relative shifting of the runners causes the angular alignment of the transverse supports in each ladder to change, thereby causing the slats resting on the transverse supports to rotate in unison about their respective longitudinal axes.
The prior art window blinds further include a tilt control mechanism mounted in the channel. The typical prior art tilt control mechanism includes a gear mounted to the tilt control rod and a second gear engageable therewith and operatively connected to a tilt control actuator. For example, a worm gear may be engageable with the gear on the tilt control rod. The worm gear may be connected to a wand extending to an elevation that can be conveniently reached by an individual desiring to adjust the tilt of the blinds.
In theory, the slats of the window blind can be tilted through an angle approaching 180 degrees. In particular, the slats may be rotated almost 90 degrees in one direction from the horizontal alignment such that the top or convex surface of each slat is facing into the room in which the blinds are mounted. Alternatively, the blinds can be rotated almost 90 degrees in an opposite direction from their horizontal alignment such that the bottom or concave surface of each slat is facing generally inwardly. In most instances, the construction of the ladders and the interference of adjacent slats will define a limit to the amount of tilting that can take place. However, excessive tilting of the slats conceivably could cause a jam within the prior art blinds. As a result, many prior art blinds include means for positively controlling the amount of tilt. Additionally, many architectural applications of window blinds specify controls on the tilt of blinds to provide a more uniform exterior appearance for a building, and to control the lines of vision from a building and/or the alignment of light directed into a building. For example, an architect may specify that window blinds be adjustable such that only the convex top surface of each slat is viewable from the exterior of the building. Similarly, an architect may specify that the slat alignments limit vision of unsightly roadways or parking lots in proximity to the building in which the prior art blinds are disposed. In some instances, the range of acceptable blind tilts may vary from one floor of the building to the next. Architects may require slat tilt limits to be controlled within a few degrees in each rotational direction.
The prior art window blinds control the amount of tilt by nonrotatably mounting a tilt control disc to the rotatable tilt control rod in the channel. A typical prior art tilt control disc is illustrated in FIG. 1. More particularly, a prior art window blind 10 includes a tilt control rod 12 of non-round cross-section rotatably mounted in a channel 14. The channel 14 is mountable adjacent the top of a window (not shown). A clip 16 is slid over the tilt control rod 12 and into the channel 14, and is frictionally retained in the channel 14. The clip 16 is stamped and formed to include a rotational stop 18 and a deformable longitudinal stop 19. The prior art tilt control disc is identified by the numeral 20 and includes a non-round central aperture 22 conforming to the non-round cross-sectional shape of the tilt control rod 12. The prior art tilt control disc 20 is slid longitudinally over the tilt control rod 12 and into proximity to the clip 16. The longitudinal stop 19 is deformed toward the tilt control rod 12 to retain the tilt control disc 20 longitudinally adjacent to the clip 16. The prior art tilt control disc 20 is cut to include a pair of angularly aligned edges 24 and 26 that are disposed and dimensioned to engage the rotational stop structure 18 within the channel 14 of the prior art blinds 10. The engagement between either of the edges 24 and 26 of the prior art tilt control disc 20 and the rotational stop structure 18 within the channel 14 prevents further rotation of the tilt control rod 12. Thus, the surfaces 24 and 26 of the prior art tilt control disc 20 can be oriented relative to the alignment of the noncircular aperture 22 therein and relative to one another to positively control the range of tilt adjustments to the prior art blind 10.
Although the prior art tilt control discs 20 have worked adequately, they have required a slow labor-intensive manufacturing process. In particular, the prior art tilt control discs 20 have been manufactured by first providing a circular washer-like disc blank having a noncircular mounting aperture extending therethrough. The circumferences of these prior art disc blanks have then manually been presented to an appropriate cutting apparatus, such as a "nibbler" which shears through the metal of the prior art disc blank to define the surfaces 24 and 26 and a reduced radius portion therebetween. The prior art disc blank generally must be repositioned several times to remove the required portions of the blank. To accurately control the range of tilts, these linear stop surfaces 24 and 26 must be accurately positioned and aligned relative to the noncircular mounting aperture 22 in the center of the disc 20 and relative to one another. This slow labor-intensive manufacturing process has added significantly to the manufacturing time and cost for the prior art blinds. Furthermore, the slow labor-intensive manufacturing process has been difficult to accurately monitor, thereby creating a significant possibility of variance from the specified configuration. Stamp forming generally is not an option because the wide range of specified tilts would require a large number of expensive stamping dies. Assembly of the prior art tilt control has been awkward and slow, with corresponding cost penalties. In particular, the clip 16 is difficult to slide into the channel 14, and assemblers frequently receive injuries on metal edges. The prior art tilt control has been even more difficult to disassemble to attend to repairs or maintenance as needed.
In view of the above, it is an object of the subject invention to provide a tilt control assembly for accurately controlling the range of tilt of the slats of window blinds.
It is another object of the subject invention to provide an efficient process for manufacturing and assembling tilt control assemblies for controlling the range of tilt of the slats of window blinds.